Circuits for automatically closing a switching transistor for a predetermined interval after a switch has been opened are very useful for rewinding a magnetic tape of a magnetic tape recorder/player for a predetermined short time period after a reproduction mode thereof has closed. According to the prior art, a capacitor is used for such a purpose by employing its charging and discharging time constant. However, the prior art is complicated and has poor reliability in that (1) an additional charging and discharging circuit is required and (2) the time change can not be negligible with respect to the electrical characteristic of the capacitor.